An example Windmill: a central grid with four outer grids pinned to its corners; the shared corner boxes (purple) are the four dark cells - shown as a box-level schematic.
Windmill Sudoku arranges five 9×9 grids as a pinwheel: a central grid shares each of its corner boxes with one of four outer grids, set at a windmill angle. Every grid is a full Sudoku, and the shared corner boxes must satisfy two grids at once.
The rule: five grids around a hub
Picture a central grid with four more grids pinned to its corners, spun like a windmill. Each shared corner box (purple above) belongs to the centre and an outer grid, tying all five together.
Solving strategy
- Attack the shared corner boxes. Each is constrained by two grids, so they crack first.
- Pass digits between grids. A value in a shared box is a given for both grids that own it.
- Solve each grid normally away from the overlaps.
- Work around the windmill. Progress in one grid opens its neighbours through the shared corners.
Common mistakes
- Forgetting a shared box serves two grids. Both must be satisfied at once.
- Not transferring digits. A corner-box value constrains the neighbouring grid immediately.
- Ignoring the ordinary rules. Every one of the five grids still needs 1-9 per row, column and box.
Can I play it here?
Not yet - Windmill Sudoku isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile:
- Try the closely related Samurai, which you can play right now.
- Browse all the Sudoku variants we do offer.
- Or print free puzzles from the printable PDF page.
Where to play it
Windmill Sudoku belongs to the overlapping family and runs on Five 9×9. It is not one SudokuStreak generates yet - but the deduction it trains is the deduction every Sudoku runs on.
Difficulty and type are two separate dials here: the type sets the extra rule, the level sets how much of the grid you start with. Easy Sudoku leaves 36 of the 81 cells filled, so there is always an obvious next move somewhere; Hard Sudoku leaves 26, where scanning gets you started and then leaves you stranded. Take it at the gentler end while the pattern is still new, and move up once it stops being a fight.